Many hard LeetCode problems are easy constraint problems
buttondown.com484 points by mpweiher 16 hours ago
484 points by mpweiher 16 hours ago
My biggest problem with leetcode type questions is that you can't ask clarifying questions. My mind just doesn't work like most do, and leetcode to some extent seems to rely on people memorizing leetcode type answers. On a few, there's enough context that I can relate real understanding of the problem to, such as the coin example in the article... for others I've seen there's not enough there for me to "get" the question/assignment.
Because of this, I've just started rejecting outright leetcode/ai interview steps... I'll do homework, shared screen, 1:1, etc, but won't do the above. I tend to fail them about half the time. It only feels worse in instances, where I wouldn't even mind the studying on leetcode types sites if they actually had decent explainers for the questions and working answers when going through them. I know this kind of defeats the challenge aspect, but learning is about 10x harder without it.
It's not a matter of skill, it's just my ability to take in certain types of problems doesn't work well. Without any chance of additional info/questions it's literally a setup to fail.
edit: I'm mostly referring to the use of AI/Automated leetcode type questions as a pre-interview screening. If you haven't seen this type of thing, good for you. I've seen too much of it. I'm fine with relatively hard questions in an actual interview with a real, live person you can talk to and ask clarifying questions.
The LC interviews are like testing people how fast they can run 100m after practice, while the real job is a slow arduous never ending jog with multiple detours and stops along the way.
But yeah that's the game you have to play now if you want the top $$$ at one of the SMEGMA companies.
I wrote (for example) my 2D game engine from scratch (3rd party libs excluded)
https://github.com/ensisoft/detonator
but would not be able to pass a LC type interview that requires multiple LC hard solutions and a couple of backflips on top. But that's fine, I've accepted that.
>The LC interviews are like testing people how fast they can run 100m after practice
Ah, but, the road to becoming good at Leetcode/100m sprint is:
>a slow arduous never ending jog with multiple detours and stops along the way
Hence Leetcode is a reasonably good test for the job. If it didn't actually work, it would've been discarded by companies long ago.
Barring a few core library teams, companies don't really care if you're any good at algorithms. They care if you can learn something well enough to become world-class competitive. If you can show that you can become excellent at one thing, there's a good chance you can become excellent at another thing.
That's basically also the reason that many Law and Med programs don't care what your major in undergrad was, just that you had a very high GPA in whatever you studied. A decent number of Music majors become MDs, for example.
But why stop there? Why not test candidates with problems they have never seen before? Or problems similar to the problems of the organization hiring? Leetcode mostly relies on memorizing patterns with a shallow understanding but shows the candidates have a gaming ability. Does that imply quality in any way? Some people argue that willing to study for leetcode shows some virtue. I very much disagree with that.
I think you have a misunderstanding. Most companies that do LC-style interviews usually show unknown problems.
Memorizing the Top 100 list from Leetcode only works for a few companies (notably and perplexingly, Meta) but doesn't for the vast majority.
Also, just solving the problem isn't enough to perform well on the interview. Getting the optimal solution is just the table stakes. There's communication, tradeoffs between alternative solutions, coding style, follow-up questions, opportunities to show off language trivia etc.
Memorizing problems is wholly not the point of Leetcode grinding at all.
In terms of memorizing "patterns", in mathematics and computer science all new discovery is just a recombination of what was already known. There's virtually no information coming from outside the system like in, say, biology or physics. The whole field is just memorized patterns being recombined in different ways to solve different problems.
It’s not about memorizing individual problems per se, but rather recognizing overall patterns and turning the process into a gameable endeavor. This can give candidates an edge, but it doesn’t necessarily demonstrate higher-level ability beyond surface familiarity with common patterns and the expectations around them. I’d understand the value if the job actually involved work similar to what's reflected in leetCode style problems, but in most cases, that couldn’t be further from reality. leetCode serves little purpose beyond measuring a candidate’s willingness to invest time and effort. That’s the only real virtue it rewards. But ultimately, I believe leetCode style interviews are measuring the wrong metric.
>a candidate’s willingness to invest time and effort
I guess it's a matter of opinion but my point is, this is probably the right metric. Arguably, the kind of people who shut up and play along with these stupid games because that's where the money is make better team players in large for-profit organizations than those who take a principled stance against ever touching Leetcode because their efforts wouldn't contribute anything to the art.
Then what if the test was how well you play chess? That takes time to study to become good. But would it be a good metric for hiring programmers?
Maybe yes maybe not, I'm leaning not but it's just an opinion. But as a company be careful what you wish for, these same candidates are often skilled at gaming systems and may leave your team as soon as they've extracted the benefits. They’re likely more interested in playing the game than in seriously solving real-world problems.
To play the devils advocate, being able to memorize patterns and recognize which patterns apply to a given problem is extremely valuable. Tons of software dev is knowing the subset of algorithms, data structures, and architecture that apply to a similar problem and being able to adapt it.
It's funny you mention that.
That's literally what CS teaches you too. Which is what "leetcode" questions are: fundamental CS problems that you'd learn about in a computer science curriculum.
It's called "reducing" one problem to another. We had an entire semester's mandatory class spend a lot of time on reducing problems. Like figuring out how you can solve a new type of question/problem with an algorithm or two that you already know from before.
Like showing that "this is just bin packing". And there are algorithms for that, which "suck" in the CS kind of sense but there are real world algorithms that are "good enough" to be usable to get shit done.
Or showing that something "doesn't work, period" by showing that it can be reduced to the halting problem (assuming that nobody has solved that yet - oh and good luck btw. if you want to try ;) )
I did quite a bit of competitive programming in school, and pretty much all the world-class competitive problems are reduced to well-known algorithms. It's quite hard to come up with something new (not proven to be unsolvable for its constraints). I believe problem setters just try to disguise a known algorithm as much as possible.
Then comes the ability/memorization to actually code it, e.g. if I knew it needs coding red-black tree I wouldn't even start.
> Leetcode mostly relies on memorizing patterns
Math is like that as well though. It's about learning all the prior axioms, laws, knowing allowed simplifications, and so on.
In the same way that writing and performing a new song is "just memorizing prior patterns and law"
or that writing a new book is the same.
I.e. it's not about that. Like sure it helps to have a base set of shared language, knowledge, and symbols, but math is so much more than just that.
In math, you usually need to prove said simplifications. So just memorizing is not enough. As you get more advanced, you then start swapping out axioms.
> If it didn't actually work, it would've been discarded by companies long ago
You're assuming that something else works better. Imagine if we were in a world where all interviewing techniques had a ton of false positives and negatives without a clear best choice. Do you expect that companies would just give up, and not hire at all, or would they pick based on other factors (e.g. minimizing the amount of effort needed on the company side to do the interviews)? Assuming you accept the premise that companies would still be trying to hire in that situation, how can you tell the difference between the world we're in now and that (maybe not-so) hypothetical one?
I never made any claims about optimality. It works (for whatever reason) hence companies continue to use it
If it didn't work, these companies wouldn't be able to function at all.
It must be the case that it works better than running a RNG on everyone who applied.
Does it mean some genius software engineer who wrote a fundamental part of the Linux kernel but never learned about Minimum Spanning Trees got filtered out? Probably. But it's okay. That guy would've been a pain in the ass anyway.
> If it didn't actually work, it would've been discarded by companies long ago.
This that I've singled out above is a very confident statement, considering that inertia in large companies is a byword at this point. Further, "work" could conceivably mean many things in this context, from "per se narrows our massive applicant pool" to "selects for factor X," X being clear only to certain management in certain sectors. Regardless, I agree with those who find it obvious that LC does not ensure a job fit for almost any real-world job.
> Hence Leetcode is a reasonably good test for the job. If it didn't actually work, it would've been discarded by companies long ago.
I see it differently. I wouldn't say it's reasonably good, I'd say it's a terrible metric that's very tenuously correlated with on the job success, but most of the other metrics for evaluating fresh grads are even worse. In the land of the blind the one eyed man is king.
> If you can show that you can become excellent at one thing, there's a good chance you can become excellent at another thing.
Eh. As someone who did tech and then medicine, a lot great doctors would make terrible software engineers and vice versa. Some things, like work ethic and organization, are going to increase your odds of success at nearly any task, but there's plenty other skills that are not nearly as transferable. For example, being good at memorizing long lists of obscure facts is a great skill for a doctor, not so much for a software engineer. Strong spatial reasoning is helpful for a software developer specializing in algorithms, but largely useless for, say, an oncologist.
> Hence Leetcode is a reasonably good test for the job. If it didn't actually work, it would've been discarded by companies long ago.
This is an appeal to tradition and a form of survivorship bias. Many successful companies have ditched LeetCode and have found other ways to effectively hire.
> If you can show that you can become excellent at one thing, there's a good chance you can become excellent at another thing.
My company uses LeetCode. All I want is sane interfaces and good documentation. It is far more likely to get something clever, broken and poorly documented than something "excellent", so something is missing for this correlation.
5 years ago you'd have a project like that, talk to someone at a company for like 30m-1hr about it, and then get an offer.
Did you mean to type 25? 5 years ago LC challenge were as, if not more, prevalent than they are today. And a single interview for a job is not something I have seen ever after 15 years in the space (and a bunch of successful OSS projects I can showcase).
I actually have the feeling it’s not as hardcore as it used to be on average. E.g. OpenAI doesn’t have a straight up LC interview even though they probably are the most sought after company. Google and MS and others still do it, but it feel like it has less weight in the final feedback than it did before. Most en-vogue startup have also ditched it for real world coding excercices.
Probably due to the fact that LC has been thoroughly gamed and is even less a useful signal than it was before.
Of course some still do, like Anthropic were you have to have a perfect score to 4 leetcode questions, automatically judged with no human contact, the worst kind of interview.
There's an entire planet of jobs that have nothing to do with leetcode. I was talking about those, not FAANG stuff. Unfortunately I am not FAANG royalty.
>Of course some still do, like Anthropic were you have to have a perfect score to 4 leetcode questions, automatically judged with no human contact, the worst kind of interview.
Should be illegal honestly.
5 years ago non-FAANG companies were fully in leetcode mode for interviews. Maybe 10-15 years ago you could totally avoid it without much problem.
It might be illegal; certainly if you can show that LC is biased against a protected class, then there would be grounds for a lawsuit.
Only if there is enough evidence. Yes, I can say that the inability to account for things like the ADA in the US can place an employer in hot water, however, since LC doesn't make those decisions, they are immune. The accountability is placed upon the employer. Don't hate the players or the game. Maybe just figure out how to fix it without harming everyone, be popular enough to make said idea into law, and get into a position of power that allows you to do so. If that sounds hard, congrats, welcome to the reason why I never got into politics. Don't even get me started on all the people you will never realize you are hurting by fixing that one single problem.
> certainly if you can show that LC is biased against a protected class, then there would be grounds for a lawsuit.
That wouldn't be hard to do. Given the disparate impact standard, everything is biased against a protected class.
> Should be illegal honestly.
I can't imagine this kind of entitlement. If you don't want to work for them, don't study leetcode. If you want to work for them (and get paid tons of money), study leetcode. This isn't a difficult aristotelian ethics/morals question.
I meant no human-in-the-loop wrt hiring, which is what I thought you were getting at.
It's the same exact thing - if some company makes you jump through hoops to get hired that you find distasteful just don't apply to company.
Not all of us are market extremists. The “invisible hand of the market” doesn’t care about human rights.
You don't know their interview process unless it's one of the big tech companies though.
No. Certain things just harm basic human dignity and should be outlawed. Judgement comes from our peers, not from machines.